Surface segregation of Sb atoms during molecular-beam epitaxy (MBE) of the InSb/InAs quantum dot nanostructures has been investigated using the reflection high-energy electron diffraction (RHEED). It has been shown that an increase of the average specular spot intensity (SSI) during growth of a cap InAs layer immediately after the surface exposure to the Sb flux is due to the presence of residual population of Sb atoms at the growth surface. The Sb surface segregation is responsible for formation of a wetting layer in the InSb QD structures obtained without intentionally deposition of InSb, when the Stranski-Krastanow growth mode is impossible. Temperature dependences of the length of Sb segregation and the Sb segregation coefficient are deduced from the RHEED SSI. The RHEED data are in a good agreement with both X-ray diffraction and potoluminescence data which confirm the presence of the InAsSb wetting layer surrounding InSb QDs. (c) 2006 Published by Elsevier B.V.